The invention relates to an absorbent product, such as a diaper, a pant diaper, an incontinence pad, a sanitary towel or the like. The absorbent product has an absorption body with a generally oblong shape including two longitudinal sides, two transverse sides, a longitudinal center line, a transverse center line, and also including a first, liquid-permeable surface layer and a second, liquid-impermeable surface layer, a liquid-impermeable backing layer, an absorption body positioned between said liquid-permeable surface layer and said backing layer, two leakage barriers made of flexible material in the longitudinal direction on each side of the longitudinal center line and the first, liquid-permeable surface layer, each of the leakage barriers having a first edge permanently fastened along the first, liquid-permeable surface layer and a second edge which extends mainly in the direction of the longitudinal center line of the absorbent product, each of the leakage barriers also having a first surface and a second surface.
In order to prevent the risk of leakage at the side edges of an absorbent product, some absorbent products have what are known as standing or raised leakage barriers, also referred to as inner liquid barriers, standing barriers or cuffs, in most cases fastened in association with a liquid-permeable surface layer on the product. The function of the leakage barrier is to prevent liquid leaking out at the edges of the absorbent product and, if appropriate, to prevent leakage of solids such as excrement. These leakage barriers are located inside the leg elastic, which shapes the product and constitutes an outer liquid barrier, also referred to as the outer leakage barrier, and are usually made of an essentially liquid-impermeable material, for example fiber fabric, which is also known as non-woven. Sometimes, the barriers can also be made of liquid-permeable material. The leakage barriers are formed by a web, one longitudinal edge of which is fastened to the absorbent product and the other, free edge of which is intended to bear against the wearer. The free edge is elastically gathered by means of an elastic thread which is incorporated into the edge of the web. Examples of absorbent articles with leakage barriers (or what are known as liquid barriers) are described in, for example, WO-A1-9207533, U.S. Pat. No. 4,695,278, U.S. Pat. No. 5,064,489, SE-T3-0264238 and GB-A-2188532. When the absorbent product has leakage barriers arranged inside flexible side flaps on both sides of the absorption body of the product, it is usual for the surface material between the two inner leakage barriers, that is to say in the liquid-receiving area, to be liquid-permeable, while the surface material outside the leakage barriers is essentially liquid-impermeable.
On diapers with what are known as inner leakage barriers, for example, the barrier will, during use, be positioned so that it bears against the leg and buttocks of the wearer and is to prevent leakage there. Each time urine is discharged into the diaper, a certain quantity comes into contact with the wearer. It takes a little time before the urine penetrates the surface layer and is absorbed in the absorbent layer, so a certain volume of urine will flow in the absorbent product on top of the surface layer. This is the volume which the barrier is to prevent leaking out at the edges of the absorbent product.
New problems arise precisely because of the purpose and material characteristics of the leakage barriers. The leakage barriers, which are essentially liquid-impermeable, can, when the product is put on the wearer, lie over the liquid-permeable surface layer instead of fitting tightly around the thighs and buttocks of the wearer. This may be as a result of the product having been tightened too firmly, incorrectly, carelessly or the like. When a leakage barrier lies incorrectly, there may be unfavourable consequences in the form of poor fit and unoptimized dimensional stability. The greatest problem, however, is in the increased risk of leakage. There are two main reasons for increased leakage, the first being that the leakage barriers are no longer positioned where they are intended to be, which can give rise to openings between the thighs of the wearer and the product, where liquid can escape. The second is that the leakage barriers can lie on the liquid-permeable surface layer and thus prevent the liquid from being admitted into and absorbed in the absorption body. Instead, the liquid runs on or via the liquid-impermeable surface of the leakage barriers, and thus gives rise to leakage and discomfort.
For bedridden wearers, the problem is marked when the person fitting the absorbent product may perhaps be unable to arrange everything properly. The wearer may be, for example, a heavy person, while the person applying the product might not have sufficient strength in order to perform all the necessary lifting and turning. This means that it is important to ensure everything is correct the first time the absorbent product is put on, so that no further action has to be taken.
The problem of leakage barriers lying incorrectly is especially marked with an absorbent product with a narrow crotch portion, that is to say the distance between the longitudinal sides of the absorption body is relatively small. The leakage barriers may then cover a greater percentage of the area of the liquid-permeable surface layer and thus indirectly of that surface of the absorption body facing the wearer than if the distance between the longitudinal sides of the absorption body is relatively great. In the same way, a high leakage barrier, that is to say a barrier where the distance between the longitudinal edges of the leakage barrier is great, can cover a greater percentage of the area of the liquid-permeable surface layer and thus indirectly of the absorption body than if the distance between the longitudinal edges of the leakage barrier is small.
An object of the invention is to solve these problems in a refined manner which is comfortable for the wearer.
According to one embodiment of the claimed invention, an absorbent product of the type mentioned in the introduction has been produced, which product essentially eliminates the problems associated with previously known such products. The first surface and/or the second surface of each leakage barrier is fastened to or near to the first, liquid-permeable surface layer and/or the second, liquid-impermeable surface layer.
According to one embodiment, the first surface and/or second surface of each said leakage barrier is temporarily fastened by a binder which loses its adhesive and/or cohesive capacity during use of the absorbent product, the first surface and/or second surface of each leakage barrier then coming away from its fastening surface and becoming a raised leakage barrier.
A binder can be an agent which has an adhesive and/or cohesive capacity, for example glue or wax, but it is also possible to use a binder such as, for example, ultrasonic welding and thermal welding.
Here and henceforth, the term fastening surface means one or more surfaces to which the binder (which is intended to lose its adhesive and/or cohesive capacity during use) is applied on the leakage barriers. The surface or surfaces where the binder is applied, that is to say the fastening surface, can in principle have any shape and be positioned in one or more different places on the leakage barriers. Here and henceforth, the term fastening surface does not therefore contain any limitation in terms of the number or shape of fastening surfaces.
It is of course impossible to avoid an interaction among various parameters, for example temperature, atmospheric humidity, choice of material, tensile forces or shear forces etc., which together contribute to a binder losing its adhesive and/or cohesive capacity, but it is in most cases possible to distinguish the major influencing factor. Here, a major influencing factor means a factor which, without the other factors, would be capable of achieving essentially the same result, although possibly after a somewhat longer time. Henceforth, a major influencing factor is a factor in which the binder loses its adhesive and/or cohesive capacity.
One type of binder in the form of a glue which will lose its adhesive and/or cohesive capacity during use is previously known from EP 0 571 548 B1. The temperature and pressure-sensitive glue in this document has what is known as a Normal Use Temperature Zone (NUTZ) which has a minimum temperature and a maximum temperature. The glue loses its adhesive and/or cohesive capacity completely or partly when the temperature either rises above the maximum temperature or falls below the minimum temperature, that is to say leaves the NUTZ range.
After the product has been fitted on the wearer, the body temperature of the wearer will raise the temperature in the absorbent product and in this way the temperature of the glue also. As a result, the temperature functions as a trigger or activating means for the glue and the leakage barriers. A suitable glue loses its adhesive and/or cohesive capacity within the range 27-40xc2x0 C., preferably within the range 29-38xc2x0 C. and most preferably within the range 30-37xc2x0 C., wherein the first and/or second surface of the leakage barriers breaks away from its fastening surfaces and become a standing or raised leakage barrier. This minimizes the risk that (as in conventional diapers, incontinence products or other absorbent products with leakage barriers) the standing leakage barriers can end up askew when the absorbent product is put on the wearer, unnecessary leakage also being avoided in this way, or that the leakage barriers can end up partly over the liquid-permeable surface layer and thus prevent liquid from escaping down to the absorption body. Therefore, in a preferred embodiment of the present invention the risk of liquid running out of the product on or via the leakage barriers has also been reduced.
Other types of binders which could be used include waxes, oils or paraffins. Certain compositions which are today commonly included in, inter alia, lotions and skincare products can also be used (this does not exclude the possibility of considering using lotions and skincare products in their entirety, for example CAREMELT(copyright), Henkel-Cognis, Sweden). Such compositions often have relatively low melting points which can easily be varied by changing the content in the composition. Suitable compositions can contain substances from groups consisting of glycerides, C14-C22 fatty alcohols, C12-C22 fatty acids and C12-C22 fatty alcohol ethoxylates with a degree of ethoxylation of roughly 2 to roughly 30, or derivatives thereof. In most cases, animal and vegetable oils contain a mixture of various saturated and unsaturated fatty acids. A person skilled in the art is very familiar with the possibility of influencing the melting point by increasing and/or decreasing the quantity of fatty acids in similar compositions, see table 1 and table 2 (values obtained from CRC Handbook of Chemistry and Physics 75th edition 1994-1995 p. 7-28, 7-29).
A suitable composition for a preferred embodiment of the present invention loses its adhesive and/or cohesive capacity within the range 27-40xc2x0 C., preferably within the range 29-38xc2x0 C. and most preferably within the range 30-37xc2x0 C.
It is also possible in a preferred embodiment of the present invention to use glue which loses its adhesive and/or cohesive capacity at TEWL values above 20 g/m2h. TEWL (transepidermal water loss) can be measured values above 20 g/m2h. TEWL (transepidermal water loss) can be measured using what is known as an evaporimeter (an EP2 from Servomed, Varberg, Sweden). The instrument is designed to measure the quantity of liquid which evaporates from the skin (in principle equivalent to the quantity transported through the skin) in g/m2h.
This value is commonly used as a measurement of the status of the skin with regard to the barrier function. However, the instrument can be used in association with products which cover the skin in order then to obtain a measurement of the moisture content on the surface of the skin (the measuring method is described in greater detail in xe2x80x9cA refined method to evaluate diapers for effectiveness in reducing skin hydrationxe2x80x94using the adult forearmxe2x80x9d, F. J. Akin et al., Skin research and technology, 1997; 3:173-176).
Instead of having a temperature-activated binder, the moisture content in the product can control the adhesive and/or cohesive properties of the binder. The moisture in an absorbent product can therefore be used in order to cause the glue to lose its adhesive and/or cohesive capacity. It is generally known that when the skin is covered by a material, the moisture content in the covered area increases. Alternatively, it is possible in a preferred embodiment of the present invention to use a glue which, when the moisture content becomes very high, that is to say equivalent to wetting of the product, loses its adhesive and/or cohesive capacity, that is to say the glue is water-soluble.
It is also possible in a preferred embodiment of the present invention to use glue which loses its adhesive and/or cohesive capacity at one or some values within the pH range 3-7. In addition to the fact that the skin has a specific pH, the pH of the urine, for example, can be used as the trigger for the glue to lose its adhesive and/or cohesive capacity.
According to another embodiment, the binder can be constituted by ultrasonic welding and/or a thermal bond of poor quality designed to lose its adhesive and/or cohesive capacity during use, for example when the product is subjected to mechanical action during use. It is also possible in a preferred embodiment of the present invention to conceive of the binder being constituted by ultrasonic welding and/or a thermal bond of good quality, executed in such a case with a smaller fastening surface than when the bond is made with poor quality. When the bond has been subjected to tensile and shear forces resulting from normal use of the absorbent product, it comes loose and loses its adhesive and/or cohesive capacity. A precondition for welding to be carried out is that materials to be welded have relatively alike melting points. Here, poor quality means, for example, a bond between two materials with relatively different melting points, that is to say, for example, that only one material melts and bonds to the other material, or that one material melts fully and the other only partly. Alternatively, it would be possible to consider that a bond of poor quality is formed when the energy supply is insufficient to melt the bonded material completely.
According to another embodiment, the binder consists of the binder of the leg elastic. When the leg elastic is fastened to the surface layers, this is usually performed using a hot-melt adhesive. If the quantity of this binder is not precisely adjusted, the binder can penetrate the surface layers in the leg portion, or escape at the edges of the leakage barriers. This excess quantity of binder can be used for fastening the leakage barriers.
According to one embodiment, the leakage barriers consist of or comprise a non-woven material or a laminate made of non-woven layers, which affords possibilities for great variation of the properties of the leakage barriers such as permeability, strength, softness and flexibility etc. A barrier laminate can of course also comprise materials other than non-woven layers, for example plastic film.